Cathepsin S and the Cat S/Cys C ratio was associated with cerebral infarction at day 1 and day 7 post-hospitalization in 202 stroke patients analyzed by Zhang et al. The investigators observed a decreasing trend at day 7 for Cat S and Cat S/Cys C, and, in contrast an increase at day 14, especially in lacunar cerebral infarcts [12]. Here, CAT is linked to brain infarction.